Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$98.42	12.238%	$110.4646	$110.46	$110.45	$110.50
Purchase #2	$182.54	7.641%	$196.4879	$196.49	$196.50	$196.50
Purchase #3	$169.81	6.737%	$181.2501	$181.25	$181.25	$181.30
Purchase #4	$54.74	10.362%	$60.4122	$60.41	$60.40	$60.40
Purchase #5	$111.84	12.756%	$126.1063	$126.11	$126.10	$126.10
Purchase #6	$198.83	7.768%	$214.2751	$214.28	$214.30	$214.30
Purchase #7	$115.61	6.588%	$123.2264	$123.23	$123.25	$123.20
7 purchase totals =	$931.79		$1,012.2226	$1,012.23	$1,012.25	$1,012.30